Characterization of the rainfall of Central Mozambique based on isotopes of water

Abstract

This paper adds to the understanding of monsoon precipitation in Southern Africa as a contribution to isotope hydrological studies in that region.Central Mozambique's climate has a wet and a dry season, both controlled by the migration of the Inter-Tropical Convergence Zone (ITCZ).Two rain collectors were installed at an altitude of 34 m and 346 m about 60 km and 120 km west of the Indian Ocean.Both were operational from 02/2007 to 09/2010.Reference is made to the IAEA/GNIP stations Harare and Antananarivo.The local meteoric water line is δD = 8.7 δ18O + 15.5‰ (R2=0.97).The mean annual rainfall in 2007-2010 is lower than for the period 1956-1984 and is most pronounced for the dry season.The observed high deuterium-excess values suggest contributions from different water vapour sources that evaporated under varying conditions over the trail of ITCZ.δ2H and δ18O ratios in dry season precipitation are more depleted in 18O due to atmospheric recycling of evaporated and equilibrated water vapour in convective systems.